Has your Persian EVER used the box successfully or can you tell if this is selective bad behavior?
Since you've been dealing with this for over a year, I feel certain you've ruled out a urinary tract infection or other health-related issue, so I won't go there.
But - I WILL say that any time a cat changes his behavior (from his normal way of acting to something less than positive, such as inappropriate litter box habits) it may be time to consult with the vet. There is normally always a good reason for the change, and the vet can help you if it is health related.
If health issues have been ruled out, what about trying different types of litter? He may not like the particular substrate you are using...try tearing up newspapers or if you have a home office paper shredder, the shredded papers work nicely also. Do you use clumping litter? I understand some cats don't like it, and refuse to use it. Mine hated it, and in fact, I had one Siamese who was less than good about "covering her business" and would walk in it and get the clumping litter all over her back feet. It resembled "concrete boots" when I tried to clean it off, and seemed to be painful between her toes. I switched back to the plain old fashioned clay-type, and have never had a problem with any of my cats until that same Siamese became elderly and developed diabetes.
It may also be marking behavior if he is not neutered yet. If there is another cat around the house, even outside not allowed to come in, sometimes males, especially when they are neutered, will begin marking to let that other cat KNOW that this space is TAKEN!
Stress may be another factor...stress in cats acts a lot like our own human adrenal response and drives the glcose levels in the blood sky-high. This assists the cat in the case of "fight or flight" by bringing the quick energy producing glucose into the blood where the muscles can uptake it for that burst if they need to fight or to run away. Is your kitty an "only" cat? Does he have plenty of toys and other activities to keep him from becoming bored and stressed? Do you ever take him outside (supervised, of course and preferably on a harness and lead) to let him sniff around? Sometimes a change in environment, even for just a short little while, can have a profound effect.
I hate to think your kitty would have to be re-homed over this problem...and I sincerely hope you get it worked out before it comes to that. I'll do some more thinking over the course of the day and post if I have any more ideas.
My continued best to you and to your fluffy little man,
Gaye and The Gang at Rosehaven Farm